This Application is a U.S. National Phase Application of PCT International Application PCT/JP98/01513.
The present invention relates to a video production system of a progressive scanning television format, and a recording and play-back equipment of the progressive scanning television format used in the same system.
A video production system employing a current interlaced scanning television (hereinafter referred to as xe2x80x9cTVxe2x80x9d) format is described hereinafter. One example of the video production systems of the interlaced scanning TV format is shown in FIG. 11.
The system comprises a camera 301 of the interlaced scanning TV format (hereinafter referred to as xe2x80x9cinterlaced scan cameraxe2x80x9d), two VTRs 302 and 303 of the interlaced scanning TV format (hereinafter referred to as xe2x80x9cinterlaced scan VTRxe2x80x9d or simply xe2x80x9cVTRxe2x80x9d), a time-code generator 4, an editing controller 5 and an interlaced scanning TV synchronizing signal source 6 (hereinafter referred to as xe2x80x9cinterlaced scan synchronizing signal sourcexe2x80x9d).
Each item of equipment in this system, except for the interlaced scan synchronizing signal source 6, are provided with interlaced scan synchronizing signal input terminals (I_REF input) 301a, 302a, 303a, 4a and 5a. The interlaced scan synchronizing signal source 6 outputs to these terminals an interlaced scan synchronizing signal that serves as a base of the system.
Timing of each of the items of equipment is controlled on the basis of this interlaced scan synchronizing signal, and the entire system is synchronized.
Also, the time-code generator 4 supplies a time-code signal from an output terminal (TC output) 4d to a time-code input terminal (EXT_TC input) 302c of the VTR 302. This time-code signal represents a signal recorded in a recording tape as a time code at the same time when a video signal is recorded.
The time-code is used later for a positional alignment of material location when executing an editing or a play back of a recorded image material.
When editing the recorded image material, the VTR 302 functions as a play back VTR, and the VTR 303 functions as a recording VTR. A part of the image material recorded on a tape in the VTR 302 is recorded again on a part of a tape in the VTR 303. In this case, the VTR 302 forwards a time-code signal from a time-code output terminal 302d (TC output) of the VTR 302 to a time-code input terminal (EXT_TC input) 303c of the VTR 303.
The editing controller 5, which is connected with the VTRs 302 and 303 by control command bus bars 7 and 8, plays back the VTR 302, records the image material in the VTR 303, and gives commands of a traveling speed of the tape and an operation of recording and play back while searching for a location according to the time-code signal recorded in the tape.
FIG. 13 shows an example of recording track pattern on a tape 412 for use with the VTRs.
There exists a helical track 440, a control track 441 and a time-code track 443 on the tape 412.
Image information is recorded on the helical track 440 aslant with the tape, and each helical track is recorded with an image equivalent to one field (for {fraction (1/60)} of a second in case of the NTSC) of interlaced TV signal. Therefore, an image equivalent for one frame (for {fraction (1/30)} of a second in case of the NTSC) of the interlaced scanning TV signal is recorded on two tracks.
The control track 441 is recorded with a marking signal 442 which indicates a location (i.e., indicating an end of a second field and a beginning of a first field) of a frame signal (to be described later).
The image signal recorded on the tape 412 is assigned with an address, or a time-code for each frame (a time-code address equals to a frame number if an input signal is the interlaced scanning TV signal). In other words, the time-code track 443 is recorded with a time-code signal. The time-code signal is a signal, which is standardized according to SMPTE12M.
FIG. 12 is a drawing depicting a flow of operation in a VTR of the prior art that records and plays back an interlaced scanning TV signal. FIG. 12 is described hereinafter by referring to FIG. 11 and FIG. 13.
During recording, a video signal is fed in at an input terminal 309, and recorded on the tape 412 after passing through a recording amplifier 310 and rotary heads 311f and 311g. One field of the video signal (every {fraction (1/60)} of a second of the video signal in case of the NTSC) is recorded on one helical track.
During play back, the video signal is picked up from the tape 412 by the rotary heads 311f and 311g, and output from an output terminal 318 after passing through a play back amplifier 317.
Numerals 313, 314, 315 and 316 represent switches for turning on a xe2x80x9cRECxe2x80x9d side during the recording and a xe2x80x9cPBxe2x80x9d side during the play back.
In the interlaced scanning TV signal, vertical synchronization signals for the first and second fields are positioned at locations, each of which lags a different number of lines from a line where an image display of the preceding field ends. By detecting the above difference, a recorded frame detector 319 detects a location of the first field from the interlaced scanning TV signal of the input terminal 309, and generates a signal to represent the location of the first field. This signal is referred to as a frame signal hereinafter. The frame signal represents the location of the first field, and it also corresponds to two fields of the interlaced scanning TV signal at the same time.
A servo circuit 320 controls a motor 321 according to the frame signal in order to advance the tape 412 at a constant speed during recording. Simultaneously, the servo circuit 320 also sends a control signal (CTL signal) which is phase-synchronized with the frame signal, to record it as a marking signal 442 on the control track 441 by a control head 324.
The control signal defined as the marking signal 442 indicates a punctuation of a frame (i.e., a position at an end of a second field and a start of a first field).
A play back frame detector 323 detects the frame signal out of the interlaced synchronization signal fed in through an interlaced synchronization signal input terminal 322 during the play back.
The servo circuit 320 controls the motor 321 to advance the tape in a manner to maintain the frame signal detected by the play back frame detector 323 to be at a fixed phase with the control signal reproduced by the control head 324.
Frame synchronization between the video signal output from an output terminal 318 and the interlaced synchronization signal from the input terminal 322 is executed in this manner, so as to achieve the frame synchronization without confusing the first field with the second field.
The time-code signal is a time-code value assigned to each of the frames of the video signal recorded on the helical track 440.
The time-code values are, for instance, a series of numbers that increase in successive order (1, 2, 3, 4, 5, . . . , etc.), and each frame of the video signal is assigned with numerals that increase successively. In case of the interlaced scanning TV signal, the time-code values are frame numbers.
During the play back, the time-code is reproduced by the time-code reader 327, and it is output from a time-code output terminal (TC output) 328 via a time-code head 326 and the switch 315.
Simultaneously, the reproduced time-code is forwarded to an external editing controller 5 through a CPU 329 and the control command bus bar 7.
The editing controller 5 ascertains that a desired location on the tape material is correctly played back by monitoring the time-code signal. The editing controller 5 outputs a command to the CPU 329 via the control command bus bar 7 for changing a tape travelling speed if there is a shift. Also, the CPU 329 outputs a phase shifting command to the servo circuit 320, and the servo circuit 320 outputs a motor control modification command to the motor 321, so as to control the play back of the desired location on the tape material.
In supplementing the description, the recorded location is controlled at {fraction (1/30)} of a second interval in the VTR using the time-code, which is added at every {fraction (1/30)} of a second, and a positional control for the two helical tracks 440 (the first field and the second field of the video signal) within the {fraction (1/30)} second interval is carried out by the control signal (this control mechanism is hereinafter referred to as xe2x80x9cframing servo-mechanismxe2x80x9d), so that no confusion in locations between the first field and the second field will take place.
On the other hand, a progressive scanning TV format, i.e. a non-interlaced scanning TV format, is now emerging as a broadcasting format of the next generation from the conventional interlaced scanning TV format.
The progressive scan TV format is briefly described here (broadcasting standards SMPTE296M and SMPTE293M may be referred for the details).
The SMPTE293M (720xc3x97483 Active Line at 59.94 Hz Progressive Scan Production Digital Representation) represents a signal configuration which is generally called 525P, and it is a promising format as the progressive scan TV format having 525 lines. The 525P contains 525 lines (483 effective lines among them) within {fraction (1/60)} of a second, and one vertical period ({fraction (1/60)} second) constitutes one frame. While a frame period of NTSC is {fraction (1/30)} of a second, the 525P does not contain information to represent a {fraction (1/30)} second punctuation.
Also, the SMPTE296M (1280xc3x97720 Scanning, Analog and Digital Representation and Analog Interface) represents a signal configuration which is generally called 720P, and it is a promising format as the progressive scan TV format for HDTV (high definition television). The 720P contains 750 lines (720 effective lines among them) within {fraction (1/60)} of a second, and one second) constitutes one frame. The 720P does not contain information to represent a {fraction (1/30)} second punctuation.
Since both formats of the 525P and the 720P have a common problem, a priority is laid on the 720P for the following description.
FIG. 9 and FIG. 10 are excerpted from the SMPTE296M. Those signals are analog signals of the 720P format and a digital signal configuration of the 720P format, and both of them are the progressive scan TV signals.
In a format of the interlaced scan TV signal, one frame of {fraction (1/30)} of a second is composed of a first field and a second field of {fraction (1/60)} second period, with different configurations of synchronization signal between the first field and the second field, and there is an information for distinguishing the first field and the second field.
However, formats of the progressive scan TV signals in FIG. 9 and FIG. 10 do not compose a field. There is no information corresponding to a {fraction (1/30)} second period.
In other words, the progressive scan TV signals do not carry any information corresponding to a {fraction (1/30)} second period.
The progressive scan TV signal shown in FIG. 10, or the digital signal of the 720P is marked with SAV and EAV. The SAV and the EAV are abbreviations of xe2x80x9cstart of Active Videoxe2x80x9d and xe2x80x9cEnd of Active Videoxe2x80x9d, to denote a start and an end of an effective picture element in each line. Also, the SAV and the EAV include identification bits of F, V and H (shown in FIG. 10). The F bit is for distinguishing between a first field and a second field, the V bit is for indicating a vertical blanking period, and the H bit is for distinguishing between the SAV and the EAV.
Although the interlaced scan TV signal for NTSC, etc. includes the F bit, which is xe2x80x9c0xe2x80x9d for the first field and xe2x80x9c1xe2x80x9d for the second field, it is always xe2x80x9c0xe2x80x9d for the progressive scan TV signal (FIG. 10). That means the progressive scan TV signal does not include any information to detect {fraction (1/30)} of a second.
For the above reason, a video production system of the progressive scan TV format can not be controlled at {fraction (1/30)} second interval, but it must be controlled at {fraction (1/60)} second interval.
A newly developed type of equipment capable of controlling with the progressive scan TV synchronization signal (hereinafter referred to as xe2x80x9cprogressing synchronization signalxe2x80x9d) is, therefore, necessary instead of the equipment for the interlaced scan TV format, in order to constitute a video production system of the progressive scan TV format. At least a camera, a VTR, a time-code generator, an editing controller and a synchronization signal source are desired which are capable of controlling with the progressing synchronization signal.
FIG. 14 is a structural drawing of a video production system of the progressive scan TV signal format composed of the newly developed type of equipment.
Referring to FIG. 14, a progressing synchronization signal source 406 generates a progressing synchronization signal for use as a basis of controlling the equipment composing the video production system. A camera 401 of the progressive scan TV format, VTRs 402 and 403 of the progressive scan TV format, a time-code generator 404 and an editing controller 405 are individually equipped with one of input terminals 401b, 402b, 403b, 404b and 405b in which the progressing synchronization signal (P_REF) generated by the progressing synchronization signal source 406 is input, so that each equipment and an entire video production system are controlled by the progressing synchronization signal.
The time-code signal generated by the time-code (TC) generator 404 is input to the VTR 402 through a time-code (EXT_TC) input terminal 402c, and the VTR 402 inputs it to the VTR 403 through a time-code input terminal 403c, so as to control locations of recording, play back and editing with the time-code assigned to each frame and each track. The entire system is controlled at {fraction (1/60)} of a second in this manner.
FIG. 15 shows an example of a tape track pattern that records the progressive scan TV format of the above case. Intervals between the marking signals showing the frame punctuation and the recorded time-codes are narrower.
As a matter of course, a cost for a complete set of this system is expensive.
A system based on the progressive scan TV signal format carries out synchronization of a prescribed frame with an interlaced synchronization signal at every two frames of the progressive scan TV signal. This is accomplished by connecting the interlaced synchronization signal which is the basis of the system to some or all of these various types of equipment that compose the system.